The Syrian opposition says it has been promised western military support in return for forming a united front, in advance of a donors’ conference in London on Friday intended to consolidate the new rebel coalition.

British diplomats said Friday’s expert-level meeting would discuss purely non-lethal aid to the National Coalition of Syrian Revolutionary and Opposition Forces, formed on Sunday in Doha, but neither the UK nor French governments are ruling out arming the opposition in the coming months in an attempt to break the bloody deadlock in Syria.

The conflict showed more signs of spreading as Israeli tanks fired at Syrian positions for the second time in as many days in response to Syria mortar fire landing on the Israeli-held Golan Heights, and a Syrian government jet bombed a rebel-held village just yards from the Turkish border.

Turkey has raised the possibility of asking Nato to deploy Patriot anti-aircraft missiles along its southern border. It has yet to put a formal request to the alliance, but Turkish officials said the latest bombing showed it was necessary for it to strengthen the defences on its southern flank. Turkey, which has about 120,000 Syrian refugees on its territory, is also pushing for expanding western backing for the rebels.